In general, capacitive touch sensors are intended to replace mechanical buttons, knobs, and other similar mechanical user interface controls. Capacitive sensors allow the elimination of complicated mechanical switches and buttons and provide reliable operation under harsh conditions. Also, capacitive sensors are widely used in modern consumer applications, providing new user interface options in the existing products.
Capacitive sensing applications may be implemented in a variety of electronic systems. Some capacitive sensing algorithms used by such systems require the initial charging of capacitive loads. FIG. 1 is a circuit diagram illustrating a conventional circuit for charging a capacitive load. With regard to FIG. 1, charging circuit 100 includes capacitive load 101, reference buffer 102, enable pin 103, and reference voltage pin 104. Charging circuit 100 begins charging capacitive load 101 when reference buffer 102 is enabled by an input received at enable pin 103. Reference buffer 102 then drives a current into capacitive load 101 until the voltage across capacitive load 101 reaches reference voltage VREF, which is applied to the reference voltage pin 104 of reference buffer 102.